1. Field of the Invention
The present invention relates to a method of testing a recording medium implemented as a WORM (Write Once Read Memory) type optical disk, and a system for practicing it. More particularly, the present invention is concerned with a method of testing a WORM type optical disk which allows high resolution picture data derived from, for example, negative films of silver halide sensitive type of photography to be sequentially recorded therein, and a system for practicing it.
2. Description of the Related Art
Today, a photo CD (Compact Disk) system is in development in which picture data are produced from, for example, films of silver halide sensitive type of photography brought by a user to a service station and then recorded in a compact disk or similar optical disk. Picture data derived from the above-mentioned kind of films have a resolution more than several ten times as high as the resolution of picture data available with other electronic recording systems, e.g., picture data output by an electronic still camera. Various approaches have been reported for recording the picture data derived from the films in an optical disk which is a miniature and large capacity recording medium, and reproducing them later, e.g., transferring them from the disk to a computer or similar processing device.
Specifically, in the photo CD system, a film scanner or similar reading device sequentially reads a plurality of picture data out of, for example, a 35 millimeters negative film. The picture data are then edited by a picture processing device, e.g., a computer for editing pictures. Finally, the edited picture data are sequentially recorded, one frame at a time, in a WORM type compact disk by a CD writer or similar recording device.
It is a common practice with a WORM type compact disk to form an intermittent guide groove, or pregroove as generally referred to, in a spiral configuration from the innermost part to the outermost part of the disk beforehand. Data are recorded in the disk along the pregroove track by track. Assume that plural frames of picture data produced from, for example, a 24-shot negative film are recorded in the disk as a unit which is generally referred to as a session. Then, in the area of a single session, a header and a subheader storing the contents of picture data to be recorded together with a reproduction program are formed in a single track, and then a plurality of tracks storing two or three frames of picture data are formed one after another. A lead-in track and a lead-out track indicative of the beginning and the end of the session, respectively, are written in the disk on opposite sides of the data area. Specifically, the lead-in track stores the recording conditions of the consecutive tracks constituting the session, e.g., the number of tracks, time information representative of the start and end addresses of each track in terms of minutes and seconds, and track information usually referred to as a table of contents (TOC).
After all the sessions have been recorded in the disk, the disk is tested to see if the data and information have been accurately recorded. If the disk is free from defects, it is handed over to the user. If the disk is defective, defects are corrected in a new disk or in the same disk if they are correctable, and then the disk is handed over to the user. A testing device or a recording device designed for rewriting data is disclosed in Japanese Patent Laid-Open Publication No. 159507/1993 or Japanese Patent Application No. 346392/1991 applied for by the same assignee as the present application. The disk once handed over to the user may again be brought to the service station together with a newly exposed negative film. Then, the pictures of the new film will be additionally written to the disk session by session after the previously recorded sessions while being spaced apart from the latter by a predetermined gap.
The conventional procedure described above has the following problem. Since additional picture data are sequentially recorded in a compact disk in consecutive groups of sessions, it is likely that the gap separating, among-others, nearby sessions has an indefinite length or that the picture data overlap at the point where the sessions join. Then, uncorrectable errors occur between nearby sessions in the event of a test. It is impossible to determine whether the uncorrectable errors are ascribable to the physical defects of the disk or the defects of .recorded data or whether they are ascribable to the juncture of nearby sessions. Uncorrectable errors occur even when the disk and recorded data both are free from defects. Therefore, it often occurs that all the sessions recorded in one disk have to be recorded in another disk all over again.